753 bobcat no reverse left side

[jdaxle]

1964Hr 753 bobcat. when it warms up loses power on the left side in reverse. been that way for several years, doesnt get used alot. seems to be getting worse. also now i noticed it seems to have a hydraulic whine where it didnt before. [maybe that is because i put a new belt and muffler on recently]. i service the filters regularly and looked at the lh case drain filter. case drain filters were replaced at about 1200hrs. inside the filter showed no metal, clean oil color but what appeares to be mummified bug parts but not alot. i dont believe it has been whining before or at least not as bad. no problems at all with the hydraulic cylinders. how do i ck for a bad motor or pump asm?

 

[OldMachinist]

Could be in the motor, pump or even a steering lever needs adjusted. If it was a steering lever problem you'd likely have a little reverse on that side. Try switching drive motors side to side and see if the problem follows the motor. If that doesn't help then the problem is in the pump, probably a replenishing valve isn't seating.

 

[Bobcatdan]

Could be in the motor, pump or even a steering lever needs adjusted. If it was a steering lever problem you'd likely have a little reverse on that side. Try switching drive motors side to side and see if the problem follows the motor. If that doesn't help then the problem is in the pump, probably a replenishing valve isn't seating.

Remove and cap the drive motor hoses at the motor. Start the engine and stroke the hydro back and forth. Dead heading the system should pull the engine down to the point of stalling in both directions. If the pump can stall the engine, the motor is problem. Vise versa, its a pump problem.

 

[jdaxle]

Remove and cap the drive motor hoses at the motor. Start the engine and stroke the hydro back and forth. Dead heading the system should pull the engine down to the point of stalling in both directions. If the pump can stall the engine, the motor is problem. Vise versa, its a pump problem.

thanks old machinist and bobcatdan for replying. sometimes when trying to back up i have to jerk lh lever several times before it moves, then it'll go full speed until i try to back drag something. then it slows down to the point where i have to raise the boom to continue.when this happens, the engine does not bog down. im also going to ck the other case drain filter for debris. based on this info, could it still be the pump or the motor? from what bobcat dan is saying im thinking that it is in the pump. either way it is going to cost me. while searching for parts, i saw where 80% of #6657024 motors are not rebuild-able. i really like the machine, just trying not to spend 4-5k

 

[jdaxle]

thanks old machinist and bobcatdan for replying. sometimes when trying to back up i have to jerk lh lever several times before it moves, then it'll go full speed until i try to back drag something. then it slows down to the point where i have to raise the boom to continue.when this happens, the engine does not bog down. im also going to ck the other case drain filter for debris. based on this info, could it still be the pump or the motor? from what bobcat dan is saying im thinking that it is in the pump. either way it is going to cost me. while searching for parts, i saw where 80% of #6657024 motors are not rebuild-able. i really like the machine, just trying not to spend 4-5k

thanks guys for replying. put new hoses on and looked at both case drains and found no metal, but there was some debris. while i had hoses off i switched drive motors and replaced motor carrier seals. now i have almost no movement forward on the rh side and have great movement in reverse. going to order new drive motors from my dealer tomorrow. does anyone have any info on the 6657024 drive motors as to why they are not available anymore or why they cannot be rebuilt. a internet rebuilder said if you can turn the output shaft by hand that it is wore out. my guess is they improved the design. thanks.

 

[Tazza]

thanks guys for replying. put new hoses on and looked at both case drains and found no metal, but there was some debris. while i had hoses off i switched drive motors and replaced motor carrier seals. now i have almost no movement forward on the rh side and have great movement in reverse. going to order new drive motors from my dealer tomorrow. does anyone have any info on the 6657024 drive motors as to why they are not available anymore or why they cannot be rebuilt. a internet rebuilder said if you can turn the output shaft by hand that it is wore out. my guess is they improved the design. thanks.

Before you order a motor, check the shuttle valve on the motor. Look for an allen headed cap. Remove it and pull out the shuttle valve pieces, ensure they move freely when putting them back together. Hopefully it will fix the issue.
A seal kit will still be available for this motor, i don't believe you need a new one, just seals or a stuck shuttle valve.
They can be rebuilt, loader parts source will be able to get the parts for that.

 

[cliffpalermo]

This thread has been very helpful but i am here to wake it up. My 753 lost left side reverse. Checked the case drain and found seal material in it. Pulled the motor replaced the seals. Have reverse under no load only. Was concerned that this was a pump issue so i swapped the lines to motor excellent forward movement when stick is pulled to reverse. This leaves me believing that the motor is still the issue. Shuttle valve was cleaned during the reseal. Anything else I should be looking for? Im having a hard time finding resources on the way these motors work so I can have a better idea on how to diagnose. Thanks in advance.

Here is a video link of forward movement with hoses reversed

 

[Jim A]

Swash plate in hydrostatic pump change angle to provide forward and reverse.
Mechanical levers do that on older machines.Check all linkages to that pump in question.
Check charge pressure should be 350+ psi .
Check that the brake pack in that motor is being released in reverse.
Switch motors left to right see if it's motor or control or main drive pump system is at fault will narrow problem down.
Good no metal in case drain filters.
Remember the brakes in drive motors are spring applied hydraulic released when motor receives pressure to move machine.
They are wet discs in oil .

 

[cliffpalermo]

So I capped both hoses and tried the levers. Pushing forward the engine trying to stall. Pulling in reverse there is more of a violent buck to the lever. Would this be how a bad bypass would respond?

Here is a video link:

 

[ward]

So I capped both hoses and tried the levers. Pushing forward the engine trying to stall. Pulling in reverse there is more of a violent buck to the lever. Would this be how a bad bypass would respond?

Here is a video link:

If it was a Gehl or John Deere or New Holland I would say the pump sounds fine under a dead head.